Method of packing homogeneous mixtures of pulverized heterogeneous materials



y 1936- P. F. 'COLLINS 2,046,367

METHOD OF PACKING HOMOGENEOUS MIXTURES OF PULVERIZED HETEROGENEOUSMATERIALS Filed March 16, 1934 2 Sheets-Sheet l IN VEN TOR mz M 60411;

'1 ;A TTORNEY July 7, 1936'. P, F, co s 2,046,367

METHOD OF PACKING HOMOGENEOUS MIXTURES OF PULVERIZED HETEROGENEOUSMATERIALS V INVENTOR nag M TTORNE Y Patented July 7, 1936 UNITED STATESATENT ()FFICE Paul Francis Collins, Columbus, Ohio, assignor to TheColumbus Dental Manufacturing Company, Columbus, Ohio, a corporationApplication March 16, 1934, Serial No. 715,977

3 Claims.

This invention relates to a method of packing homogeneous mixtures ofpulverized heterogeneous materials, and the main object of the inventionis to provide a method of packing in containers pulverized homogeneousmixtures, composed of different materials having difierent specificgravities, and/or different grain sizes, and preventing the samefrom-classifying themselves into strata, as a result of agitation andshifting during storage, shipment or handling of the filled containers.

Heretofore it has been a common practice in the manufacture andpackaging of such mixtures to use containers which are somewhatoversized,

' so that a given weight of the material packed into a container will bemore or less loosely confined. When materials of this nature, so packaged, are ultimately received by the consumer, following the averageamount of storage, shipment and handling, the container, due to settlingof the particles of the mixture, is only about 80% filled. This settlingof the contents of the container resulting from the vibration andjarring of the container tends to cause the ingredients of the mixtureto separate, those having the highest specific gravity, and/ or thesmaller grain sizes, to settle to the bottom, whereas those ingredientswhich have intermediate specific gravities, and/or intermediate grainsize, to classify themselves more or less in the central area of thecontainer in strata, while the ingredients of least specific gravity,and/or largest grain size, tend to classify themselves and take aposition in strata near the top of the container.

As a general rule, substantially all of these pulverized homogeneousmixtures require careful preparation by the manufacturer in regard tothe selection of proper raw materials, the proper grinding and grainsize of each of the ingredients, and the proper proportion or weight ofeach of the ingredients and their processing through machines which willinsure a homogeneous mixture of the ingredients. To make certain thatthe materials are properly mixed and used, it is the other attempts madeby the manufacturers of such products to insure the furnishing of theproducts in proper condition for successful specified uses, such effortsare largely nullified and rendered ineffective because of the methodsheretofore employed in packaging such compositions in their containers.

It has been found that when using such packaged materials in some of thearts, the upper strata of the mixtures behave differently and havedifferent physical properties than the middle and/or lower strata. Thisresults in trouble and the impossibility of obtaining regular results inthe function of these pulverized mixtures. In some cases, where themanufacturers are aware of the settling out and classifying of theingredients of their mixtures into separate strata, printed instructionsto prospective users are given on the container labels to shake, andeffect a reblending of the ingredients thoroughly before using. Itfrequently happens, however, that a proper reblending cannot be carriedout without the use of apparatuswith which the user is unprovided, orwithout the use of technical knowledge in reblending which only theparticular manufacturer can have, as a result of which the user of thematerial cannot depend upon the material giving the reliable, and oftenprecise results, necessary for him to obtain in his work in order tosatisfy his customers or clientele.

As an example of homogeneous mixtures of pulverized heterogeneousmaterials, attention may be called to dental investment compounds. Thesecompounds are used by dentists and laboratory men (mechanical dentists)in the process of making precision inlays, plates, bridges,

etc., for the human mouth. These compounds vary in their composition towidely different degrees, some being made for the purpose of being usedin the construction of models, others for the purpose of casting inlays,bridges, etc., and still others for solder and like work in' dentistry.Such investments usually contain a binder and a refractory material andlesser quantities of various modifying agents. The binders commonly usedare gypsum products, such as plaster-of- Paris and alpha-gypsum, and therefractory materials commonly used are some forms of silica, such ascrystalline quartz or cristobalite, with which are frequently combinedsuch other ingredients as graphitaasbestos fiber and pumice stone. Themodifying ingredients may be accelerators, such as potassium sulphateand sodium chloride, or retarders, such as glue and dextrin forrespectively hastening orretarding V the setting of the gypsum binder;also materials which aid thermal expansion of the investment mix, suchasboric acid, and such other ingredi ents as may be used to identify aparticular manf r As an illustration in the useof casting investments indentistry, the following procedureis re sorted to: The dentist preparesa cavity in a natural tooth for agold inlay; Wax is then pressedinto thecavity and. the outer surfaces" modeled and contoured in precise detailsThe wax pattern is removed, impaled upon a spriie pin and throughcommonprocedureinthe art is surrounded with'a wet'investment mix. By thetime theinvestment mix has completely set up and hardened, expansion(setting expansion) has takenplace,

investment subjected to an elevated temperature The sprue pin is removedand the suificient to dissipate the wax pattern 'and'ex- Vpand (thermalexpansion) the investment. This leaves an expanded wax pattern cavity inthe'in- V V I eterior of the investment into'which molten castmanufacturer usually recommends certain pre.

sprue pin. V a

, In general, dental gold alloys for casting undergo-about 1.25 percentshrinkage while cooling from theirmolten state to their solid state; In

an attempt to compensate for this shrinkage of the gold' alloy, allinvestment ma'nufacturers have 1' made an effort to produce productswhereintheir setting expansion plus their thermal expansion, hence theirtotal expansion, wouldequalthe gold shrinkage. To further gain theseendsythe ferred percentages of water which shalladded to the pulverizedinvestment mixture a preferred I 'length of 'time forthe mix'to set-up(settingexperatures for thermal expansion. These -prepansion), andcertain preferred elevatedtemferred: recommendations are necessarybecause the present known ingredient materials that go *to" make up theinvestment mixtures possess a rather fixed physical properties, andthe-ingredients must be blended homogeneously within comparativelynarrow ranges to preserve the severa l requirements of the art,resulting in the agg-regate mixture being more or less inflexible. In

cases where these mixtures have classified th'emj selves into stratasetting, expansion varies, decidedly, also thermal expansion, andmoreover, the

sum total of both setting and thermal'expansion react irregularly.Further, such classified mixtures present marked variations in thehardness and refractoriness of the investment. In such Iinstancesffonexample, one'portion of the container between top and bottom presentsamixture high in the percentage of quartz; in another portion themixture is high in the p e'rcen'tagerof gypsum. 'Wherethe quartzpercentage ishigh the setting expansion is :decreased; the thermalexpansion is increased; thetbtal expansion is in- P creasedand' thestrength and hardness impaired. Where the gypsum percentage'is high, thesetting expansion is increased; the thermal expansion is Investmentmixtures packaged for soldering and model* work have also reactedirregularly, because of thetendency of the ingredients to sep- *aratefrom a homogeneous mixture Thenon-homogeneity of the dental investment 7mixtures has been costly to the dentist, to the ing gold is "forcedthrough the holeleft by the ally, I preferr three steps.

mechanical dentist and to the patient. It has been costly to the dentistin the, prevalence, of

ill-fitting restorations which had to be made over,

resulting, in loss of labor, time, materials and in someinstances,hisiclientele. To the mechanical dentist it has'meant the lossof labor,time,

materials and. often the good-will of the dentist.

ly fitted restorations in as much as the dentist ,could not produce moreaccurate structures because of theirregular behaviorof the dentalinvestments.

'In packing homogeneous mixtures ofipulverized heterogeneous materialsby my method I overcome all of these disadvantages; In carrying V out myprocess, generally, I prepare a homogena eous mixture andpack it underpressure in con tainersr Theamlount of pressure and the number of thesteps oi' filling and pressing in individual containers are dependentchiefly on the shape of the pulverized grains, the fineness of the grainsize, the specific gravity of the ingredients, and the shape and size ofthe containers.

Where theshape of the individual grainis somewhat angular with thecorners and edges tending to'be sharp, a moderate amountof pressure isemployed. Under such conditions, small,

wide mouth containers andismalhopen end drums can usually be packedwithone filling and one pressing, whereas large containers, large,

drums and: odd shaped containers may require two steps; for example, 60ito percent of the 'mixture is' placedinthe container, then pressed,

next add the remaining portion of the mixture, I

then press and-seal.

-Where the shape of the individual "grain is somewhat boulder-likewith'corners andedg'es. I tending: tobe smooth and roundedgreater pressure isemployed and usually a greater number; of steps of'filling and pressingare required for:

each-individual container. Generally stated, the amount of pressure andthe number of. the steps offilling and pressing are largely influencedby dients and also by thesize'of the grains (degree of pulverization),and the shape of the different grains.

. the differential of specific gravity of theingre In carrying outmymethod inidental invest through 200 mesh-screens I employ pressure 1from about 1 to 10 pounds per square inch" for containers withcapacities of from Ito 25 pounds.

instance.*' V ,7 V: V

fWhere large containers, such as drums ranging upward of 25 poundscontent, are used mas sociation with dental investments, goodresults canbe obtained by using the same relative pres 'Iprefer'to employ two'steps' in packing in this 7 sure,.as in the instance of smallcontainers. In

association. wlthsuch pressure onestep, by my decreasedjthe totalexpansion is decreased; and method pmduces good results although'vgienrathe refractoriness impaired.

- With my method ofpacking under pressurei I firmly support each grainwith a generally equalized pressure from other surrounding grains.

.The containers are. so selected as to size and the lids so seated as tosubstantially hold-the equalized support of the grains. By my method,homogeneity of the dental mixture is maintained and the uniformity ofthe contents of the container is substantially constant from top tobottom irrespective of the storage, shipping and handling commonlypracticed.

In the accompanying drawings I have shown certain means for carrying mymethod into practical efiect, without, however, restricting theinvention .to the particular meanswhich, for example, I .have set forth.In these drawings:-

Fig. 1 is aside elevation of a form of packing press which may be usedin carrying out the process.

Fig. 2 is a front elevation of the same.

Fig. 3 is a perspective view of a type of container which may beemployed. Fig. 4 is a perspective view of the bed or platform of thepress and a container or workholder mounted thereon, the workholderbeing shown in open position.

Fig. 5 is a view similar to Fig. 4 showing a first filling step.

Fig. 6 is a sectional view through the container as it appears after thefirst filling step and with the press plunger in position for a firstpressing action.

Fig. '7 is a view similarto Fig. 6 showing the condition of the materialin the container after the first pressing action.

Figs. 8, 9 and 10 are views similar to Figs. 6 and 7, showing,respectively, a second or final filling operation, and second and thirdpressing operations.

Fig. 11 is a sectional view through the packed and sealed container.

The container 1 may be of any suitable form and size for holding thematerial in quantities of from 1 to 25 pounds or more and, as shown in.the present instance, is of that type comprising a rectangular bodyportion having a top wall 2 provided with a'mouth or'opening 3 of lessdiameter than the diameter of the container, which container is adaptedto be closed by a cover or seal 4 having a depressed center or funnelportion 5 adapted to fill the opening 3 and extend downwardly a slightdistance into the container and having a flange portion 6 which overlapsthe wall 2 in the closed condition of said seal or cover. In packing thecontainer I according to my improved method, the container is preferablyplaced upon the bed or platform] of a suitable press 8, the platform Iof which is provided with a clamp or workholder 9 having hinged jaws ormembers movable to closed position to clamp the container and to openposition to release it and adapted to be held in closed position by anysuitable type of latch or fastening means 10.

In the operation of filling the container I, the container is clampedfirmly in position by the holder 9 and a filling funnel II is thenapplied thereto, as shown in Fig. 5. This funnel is provided with alower cylindrical portion I2 and an upper conical portion 1 3,said'portion [2 being provided a short distance above its lower edgewith a'supporting flange HI to rest upon the container top 2 andsupport-the'funnel in position, leaving the said lower edge of theportion l2 projecting in the form of a retaining projection l5 whichfits within the opening 3 and centers the funnel therein. Through thisfunnel the mixture is introduced into the container from a suitablesource of supply through a chute or other conductor IS. The amount ofthe material l1 thus introduced on the first filling action into thecontainer is less than that to be packed therein, but constitutes amajor proportion of the amount to be packed, and, owing to its loosecondition, this material loosely fills all of the container except aspace, beneath the top wall 2 surrounding the opening 3 and extendsupwardly above the top of the container to a certain elevation withinthe funnel II.

The material I! so supplied to the container I is then subjected toinitial compression by means of a compressing plunger it having aconical lower end or compressing portion 19. This plunger is forceddownward through the funnel and to a sufficient depth into the containerto displace that portion of the material which is within the funnel andforce it downwardly into the container and compress or condense thematerial in the container to the desired degree of pressure ordensity.In this action the conical portion IQ .of the plunger acts to displaceand exert pressure in all directions radially toward the side walls ofthe container as well as to exert downward and upward pressure, suchupward pressure causing the material to fill the void or spacepreviously existing at the top of the container beneath the wall 2 andaround the opening 3. This first pressing operation being completed, theplunger I8 is withdrawn from the container, as shown in Fig. 7, with theresult that there is left within the container the initial charge oramount of material in compressed condition and having formed therein acavity 2!] which is of conical shape at its lower portion andcylindrical shape at its upper portion conforming to the contour of theportion I9 .and lower part of the cylindrical body portion of theplungerl8. This operation obviously effects the filling of the upper portion ofthe container beneath the wall 2by radial and upward displacement ofportions of the initialcharge of the material. I

Upon withdrawal of the plunger [8 at the close of this first pressingoperation, the remainder of the material to complete the charge is thensupplied through the conductor I5, as shown in Fig. 8, to fill thecavity 20 and this material in its loose or unpacked condition extendsto a certain level upwardly in the funnel H, as shown in Fig. 9. Aplunger 2! of cylindrical form to snugly fit the cylindrical part of thefunnel is then substituted for the plunger !8 and, through the action ofthe press, is forced downwardly through the furmel and to a slightdegree below the container wall 2 to displace the second charge of thematerial and pack it in the container so that the material filling thecavity 28 will be packed under the same degree of pressure as theoriginal charge, and at the close of this operation the plunger 21 andthe funnel ll are removed. The container is then in condition to besealed or to have its cover 4 applied, and in such condition thecon-tainer is filled with the material at all points except immediatelybelow and in line with the opening 3 where the material terminates justbelow the opening to provide a recess 22 to receive the depressedportion of the lid or cover 4. This lid or cover 4 is then applied toseal the opening 3 and its portion 5 extends downwardly into and closesthe recess 22 and the force with which this cover is fitted in positionresults in the continued application to the packed material through thecover of pressure conforming to that under which it was packed orsufiicient to maintain the packed rial; is packed under such pressurethat it can not "material in i its compressed condition againstVmovement or shifting in any direction to cause separation ofits-different components according to their diiferent specificigravities. Eachplunger lf8-and M is carriedby a'rack bar 23 slidablymounted on the preset and movable by suitable gearing "actuatedbyanoperatinghandle 2 whereby the plunger may be raisedand lowered and inits pressing action caused. totexert an exact degree of pressure on'thematerial, and the plunger of each type is detachably mounted so thatthe'other type of plunger may be substituted quickly and convenientlyfor use in its place.

The result of the operation of packingthe material in the container I inthe manner above'described is to provide a packed container holding adefinite amount of material in which the matepossibly shift as a resultof movements or agitation due to storing, shipping or handling, so thatwhen the container is opened for use the compoundwill be available foruse in exacttcondition of mixture in which its" components'were combinedfor use by the manufacturer to meet the l most highly technicalconditions required to secure desired-results. Hence by my methodcompositions or mixtures of materials'of different specific'gravitiesmay be combined in the exact manner necessary-forecertain' definite usesand functions and handled; shipped and-stored without change of positionof its different ingredients; so

use :of definite mixtures. e

- that the manufacturer and user may be assured that a mi xture designedto have certain working properties may be employed by the'user to securefunctions conferred by such properties so that invariable results mayalwaysjbe obtained by the As" stated, the steps of the method as abovedescribed are preferably employed, but that the amount of pressure used,the number of pressure steps employed, and the amountsof the materialsupplied to the container for successive pressure steps maybevaried'according to the1character of the compositions'tobe packed,theform and size of the containers used, andother controlling factors; 7

WhatIc1aimis:--l j V j 1. The method of packing incontainers dentalinvestment compounds in the form of granular aggregates of" differentmaterials which differ in grain size, shape or specific gravity andwhich are so mixed as toinsure specific and uniform reactions' of allparts of the compoundin'said conv tainer under the various conditions towhich such compositions are subjected in the use thereof; and wherebyStratification separationof ,thecomponents of the packed mixture underdisturbing forces is prevented, :Which comprises'compo'unding f'amixture having predetermined physical properties for aspecified use;introducing the "compound into the container in the properly mixedstate,forcing a plunger with a straight-line movement into said container tocompact the compound to a degree'that will substantially prei ventmigration of the grain and Stratification 'separation of the componentsof the compound 7 from their initial properly mixed state underdisturbing forces, and then'applying a' closure to such container sothat it exerts suflicient pressure vent migration of the; grains andstra'tification -upon the packedi compound to maintain it substantiallyin its initial compacted state 2. The method of packing in containersdental i V 7 investment compounds. in the form of granular aggregates ofdifferent materials which diflerjin- 5 grain size, shape: or :specificgravity and which are so mixed asto, insure specific and uniformreaction of all parts of the compoundin said container under the variousconditions t whIchsuch j compounds are subjected in the use thereoL'andwhereby Stratification separation of the com o nents 'of the packedmixture under disturbing forces is prevented, whichcornprises compoundin'g a mixture having "predetermined Physical properties forafspecified'use, introducing the com pound into a container having aflange forming a part of the top wall with an aperture therein'for thereceipt of a friction top, i'ntroducingthecom f pound into thecontainervinthe properly mixed? state,. forcing the conical end of aplunger into [the compound with a straight-line movement so as tocompact suchcompound against'the bottom and side, walls and against theundersurface of said flange to a degree that will substantiallypreapplying the friction top to such containerso that it exerts'sufiicient pressure upon; such packed material totmaintain itsubstantially in itsinitial compacted state. 7

3. The method-of packing in containers dental investment compounds-inthe form ofgranular 40 aggregates of different materials which-differ ingrain size, shape or specific'gravity andwhich are j N so'mixed as toinsure specific and uniform reaction of all parts of the compound insaid con- 1 tainerunder the-various conditions to which suchcompoundstare subjected in the use' thereof and whereby Stratificationseparation of the compo-' nents 'ofthe packedjmixture under disturbingforces is prevented, which comprises introducing the compound in'to a"container having ,a hedge forming a part of the top wall with anaperture therein for'the receipt of a. friction top, intro;-

*ducing the compound into the container in a properly mixed state,forcing the conical endof a plunger into the compound with astraight-line movement' so as to compact such; compound, against thebottomand side walls andagainstv 'the undersurface of said; flange-to adegree that will substantially prevent migration of the grains andstratification separation of the components q of the compound from theirinitial properly mixed state under disturbing forces, 7 and; forcing"the V cylindricalend of aplungeragainst said material with astraight-line movement to finally compact it, and then applying the.frictionytop to such container so that it exerts suflicient pressureupon such packed material to maintain itsubstantially V in its initialcompacted state; V V

PAUL FRANCIS GOLLINS.;

